In recent years, the cockpits of modern aircraft have become increasing crowded with complex avionics equipment, which provide the flight crew with much needed information, while concomitantly requiring increased crew attention. Consequently, it is quite beneficial to provide automatic control systems, for relieveing some of the pilots many inflight tasks. Autopilots, which automatically manage the aircraft control surfaces, are typically some of these automatic systems.
In the past, autopilot systems have provided for short term yaw damping by controlling rudder position. These prior art systems typically used a gyro to generate yaw rate information, which would then be converted into a rudder position command signal and then applied to the rudder, in combination with a rudder position feedback loop.
While these systems, or variations of them, have been extensively used for yaw damping, they do have numerous serious drawbacks. One particular problem, is that the long term yaw coordination has been typically left to the pilot. Furthermore, the steps that the pilot would take to correct the long term yaw coordination would typically involve trimming the aircraft. These steps frequently would be opposed by the short term yaw damping and rudder servo position feedback of the automatic pilot. As a result, pilots frequenly would disengage the automatic pilot, trim the aircraft, and then reengage the automatic pilot with the new trim configuration. This digengaging and reengaging causes unwanted distractions in the cockpit.
Consequently, a great need exists for improvement in autopilot systems which assists in the control of yaw of the aircraft, for both short term yaw and long term yaw coordination, without opposing any pilot initiated rudder adjustments.